Characterization of microbial methanol metabolism

Background.

A number of microorganisms have evolved pathways to utilize one-carbon substrates like methanol as sources for energy and carbon (Anthony 1991). Among them methylotrophic bacteria and yeasts share the common pathway that methanol is first oxidized to formaldehyde and then either assimilated via glyceraldehyde-3-phosphate, or further oxidized to CO2 for energy production. Assimilation further uses intermediates of gluconeogenesis and sugar phosphates to create the sugars needed for cellular growth (Russmayer et al. 2015).

The major difference between yeasts and bacteria is the first step, oxidation of methanol. Yeasts use alcohol oxidases (EC 1.1.3.13, prosthetic group: FAD) for this step which transfer the electrons to oxygen while most methylotrophic bacteria use NAD(P)+ dependent alcohol dehydrogenases (EC 1.1.1.2, cofactor: Zn2+) which transfer electrons to NAD+ or NADP+, respectively. This has major physiological consequences: alcohol oxidases cannot make use of the energy and reductive power that is liberated by oxidation of methanol. Consequently large amounts of metabolic heat are liberated, and the biomass on methanol is only about half of the theoretic yield (Mattanovich et al. 2014).

Aims and methods.

The objectives of this project are to study the differences of bacterial and yeast methanol metabolism by

(1) characterizing respective methanol oxidizing enzymes and

(2) unifying both pathways in one system.

The metabolic impact of different methanol oxidizing enzymes will be characterized, and the difference in metabolic heat production, oxygen consumption and carbon flux will be quantified.

Anthony, C. (1991) Assimilation of carbon by methylotrophs. Biotechnology 18, 79–109
Russmayer H, Buchetics M, Gruber C, Valli M, Grillitsch K, Modarres G, Guerrasio R, Klavins K, Neubauer S, Drexler H, Steiger M, Troyer C, Al Chalabi A, Krebiehl G, Sonntag D, Zellnig G, Daum G, Graf AB, Altmann F, Koellensperger G, Hann S, Sauer M, Mattanovich D, Gasser B. (2015) Systems-level organization of yeast methylotrophic lifestyle. BMC Biol. 13:80
Mattanovich, D., Jungo, C., Wenger, J., Dabros, M., Maurer, M. (2014) Yeast Suspension Culture. In: Hans-Peter Meyer, Diego Schmidhalter (Eds) Industrial Scale Suspension Culture of Living Cells, Wiley-Blackwell